TEHERAN (AFP) - Iran and the United States will on Monday and Tuesday hold their first direct talks in decades, in an unprecedented move toward securing a comprehensive nuclear deal between Teheran and the West.

The discussions will take place in Geneva, with the US delegation led by Deputy Secretary of State Bill Burns and Undersecretary Wendy Sherman, who is responsible for Iran negotiations.

Iran will be represented at vice-foreign minister level in what is the most senior direct bilateral contact on the nuclear issue so far.

The talks will be the first between Iran and the US to fall outside the P5+1 group - Britain, China, France, Russia, the United States plus Germany - which is pursuing talks in the quest for a landmark nuclear settlement.

Mr Jake Sullivan, National Security Adviser and Deputy Assistant to US President Barack Obama will join the US team.

Ms Helga Schmid, the political director of the EU which has been overseeing the nuclear talks with Iran, will also join, the European Union said in a statement.

A senior US administration official said the latest developments signal that "the talks are intensifying." The meeting is "a timely opportunity" to make progress, the US official said, stressed however that the talks would be "consultations" that would feed into the P5+1 process, which resumes between June 16-20 in Vienna.

Iran and the US, at odds since the 1979 Islamic revolution and the hostage crisis that followed, have in the past year taken tentative steps to rapprochement.

President Hassan Rouhani, a self-declared moderate elected last June, spoke by telephone with Mr Obama shortly after taking office.

Such a step had not occurred since the revolution and would have been considered unthinkable under Mr Rouhani's predecessor Mahmoud Ahmadinejad, under whom relations with the West plummeted.

US Secretary of State John Kerry also briefly met Iran's Foreign Minister Mohammad Javad Zarif in Geneva last year. The apparent thaw is aimed at ending decades of enmity, with an agreement on Iran's nuclear activities the main prize sought by the US and other world powers.

In return, Iran wants an end to wide-ranging economic sanctions, imposed as punishment for its atomic programme and resisting extensive international inspections, that devastated its economy.

In Saturday's announcement the foreign ministry also said two days of direct talks with Russia in Rome would immediately follow the US discussions.

A French diplomat told AFP that the Geneva meeting concerned specific issues over sanctions between Iran and the US and that other P5+1 members had been consulted.

Iran's meetings with the US and Russia will be interpreted as the start of an all-out diplomatic push to close glaring gaps that officials from both Teheran and major powers nations have said are blocking a deal.

Iran is also "working to arrange" bilateral discussions with remaining members of the P5+1 before the next meeting in Vienna, the ministry said.

The talks are aimed at securing a final deal ahead of a July 20 deadline imposed under an interim agreement last November, under which the US and its partners released US$7 billion (S$8.8 billion) from frozen funds in return for a slowdown in Iran's controversial uranium enrichment programme.

Iran has consistently denied it is seeking nuclear weapons but wants an independent atomic energy programme and has repeatedly defended its right to enrich uranium for peaceful purposes.

But Israel and lawmakers in the US Congress have repeatedly warned against lowering the pressure - in the form of sanctions - on Iran.

Several rounds of talks have already been held in Vienna but the latest in mid-May ended with no apparent progress. Iran within days urged western powers to resist influence from third parties not directly involved in the negotiations, in a clear reference to Israel.

Major issues between Iran and the P5+1 remain outstanding.

These reportedly include the scope of Iran's enrichment of uranium, which if further purified could be used to trigger a nuclear explosion, and its unfinished Arak research reactor, whose by-product waste could provide an alternative route to an atomic bomb.

Failure to nail down a conclusive deal could have calamitous consequences, potentially sparking conflict - neither Israel nor the United States rules out military action.